Topic 10: Avian diseases caused by circovirus, Chicken infectious anemia

Question 1

Avian Circoviruses

Answer 1

Circoviridae, Genus circovirus
- PBFDV, PiCV, GoCV

Genus gyrovirus
- CAV, chicken infectious anemia

Question 2

PBFDV - Epidemiology

Answer 2

Australia, 1984, most prevalent in austarralian species, eg cockatoos

Young psittacine birds (old and new world parts) under 3 years susceptible

Horizontal and vertical transmission

vertical acquired from nestlings of the parents fo germinative

horizontal from other flock members

Virus can be found, spread through crop secretions (crop milk), faeces and feather follicles and skin particles

Adult birds develop resistance when infected, but will be life long shedders

sound birds more susceptible, weaker immune system

Question 3

Pathogenesis PBFDV

Answer 3

infection, viraemia, reaches all organs

attacks feather follicles and dividing cells of beak and claws, progressive beak feather and claw malformation nd necrosis

later, feather shaft constriction hampers feather development until al death growth stops

also causes degeneration of lymphoid tissues, thymus and bursa fabricci , immunosuppression, 2º infection

locus minors resistência, beak and claw lesions

also affects the gut epithelial cells, vom , dra

Question 4

CS of PBFDV

Answer 4

Young psittacines, under 3 yrs susceptible
- specifically at 2-10w
acute form
- lethargy anorexia, vom, dra, nasal discharge
- depression, inappetence
- severe immunosuppression , multiple 2ºinfections, dead within 2-4 weeks, typically before lesions on beak and
- 10-70% losses

Chronic
- may last for years
- if the bird manages to mount an immune sresponse
characteirics changes after 1st moult, require time to develop
- loss of feathers, broken beak, soft beak, no feather son neck or back

Surviing birds are lifelong shedders

Question 5

Dx of PBFDV

Answer 5

CS, PM Lesions and HP
avian circoviruses cannot be cultured!

PCR, nucleotide sequence

Cross infections with other genotypes of other birds, goose, duck pidgeon etc

different pathogenicity

Question 6

Tx of PBFDV

Answer 6

no Tx, only treat 2º infection,

Euthanisa recommended

Question 7

Prevention of PBFDV

Answer 7

hygiene
prevention 2º infection with ab 
Vx with inactivated virus 
quartile new birds and test 
known carrier should not be introduced to new pens

Question 8

PiCV Epidemiology

Answer 8

NA, 1993, now WW

Young pigeon, mostly under 1 year ( esp. up to 4m)
–> Young pigeon disease syndrome, YPDS

Germinative
Horizontal, spread through the droppings or by inhalation

Question 9

PiCV Pathogenesis

Answer 9

Targets lymphoid organs, thymus, spleen, bone marrow, bursa fab. –> Immunosuppression, failure to overcome 2º , common or harmless infection

Question 10

CS / Symptoms PiCV

Answer 10

Generalised no specific lesions, similar BFD, lethargy, anorexia, WL, dra, resp

Death within 2-5 days (can be 100% mortality in young pigeons

Retarded growth

Rarely beak, claw and feather deformities

Poor performance (racing)

symptoms depend on the severity of the 2º infection, age of infection

Infection can be asymptomatic

Question 11

Dx of PiCV

Answer 11

PCR of internal organs (PM), faeces

Question 12

Tx of PiCV

Answer 12

no Tx, only of 2º infection

Question 13

Prevention

Answer 13

Prevent contact with virus, hygiene, quarrantine etc

Question 14

GoCV, Goose Circovirus

Answer 14

GoCV, affects geese under 1w, growth retardation, decreased production, feathering problems, increased mortality due to 2º infections

Co infections with Riemerella anatipestifier and aspergillum fumigates can occur

Question 15

CAV Aetiology

Answer 15

Japan, 1979, now WW esp countries where chickens are raised commercially

causes anemia and immunosuppression

Single serotype, only chickens affected

Circoviridae, Gyrovirus

• genome codes for 3 VP , viral proteins
• VP1, capsid proteins
• VP1 and 2, protein phosphatase
• VP3, induces apoptosis in infected cells

resistance, 80º up to 30 mins

Question 16

CAV Epidemiology

Answer 16

Horizontal, faeco oral, respiratory via infected feather follicle epithelium

Vertical, via egg, semen of roosters

vx of seronegative flocks before onset of egg production is recommenced to prevent vertical transmission

Virus is shed via the egg and faeces for up to 2 months (max shedding week 2 PI)

maternal ab negative chicks are susceptible to disease until 3w

postive are protected

under 3 weeks, disease, sever imuunosuprrseion
over 3w, no disease, mild immunosuprrseion

Question 17

CAV Pathogenesis

Answer 17

PO, Intestine, fireman, within 24hrs, to organs and tissues

Bone marrow, erythroid and myeloid cells, anemia, immunosupression

thymus, Bursa fabricius, immunosupression

Platelets, haemorrhages, lymphoid cell necrosis

other organs

Immunosuprrseions leave the bird liable to 2º infection
- E.coli, mycoplasma, adenoviruses, reoviruses

Question 18

CS CAV

Answer 18

Clincialy affected birds, anemia dermatitis syndrome in 10-14 day old chicks, rare,following vertical or horizontal transmission

Sub clinical: after horizontal, resistance develops with age, decreased productivity

Most susceptible are MAtab negative, 1-4 w

incubation of 7-10d

clinical disease only apparent in ab negative chicks up to 1m

Atypical signs, anorexic chicks, lethargic, inappetence, depressed and pale with anema, low icv, blood may be watery and clot slowly

retarded growth

Variable mortality, 10-50% , higher with 2º infection

Question 19

Pathology of CAV

Answer 19

pale tissues, haemorrhages thought the body
anemia, oedema, haemorrhages, under skin, gizzard, proventriculs

atrophy of the bursa and thymus 10-14 days after vertical transmission

pale and yellow bone marrow

necrotic regions in the liver

Question 20

HP of CAV

Answer 20

myeloid and lymphoid cell depletion

Question 21

Dx of CAV

Answer 21

Cs, pathology, gross lesions, only suspicion of disease, need further diagnostic testing

culture in chicken lymphoblast cell line and chicken embryos

virus isolation in lymphoid cell cultures

IF, PCR, VN, ELISA, IP

Question 22

Ddx of CAV

Answer 22

Infectious bursa disease, (dra, more intense bleeding, thymus only mildly affected)

Newcastle DV

inclusion body hepatitis, necrosis, bleeding, pancreas liver and spleen

Question 23

Tx of CAV

Answer 23

no treatment, only 2º bacterial infection

Question 24

Prevention and control

Answer 24

general preventative ruiles, hygiene

Vx via drinking water at 12-15 days
- live (moderately attenuated vx) fo Ab negative breeder flocks @ 12-15 w , prior to egg production

IM/SC vx over 2w, but min 6 weeks before laying